1. Field of the Invention
This invention relates to the making of polyurethane compositions, useful for making castings of noncellular, thermosetting polyurethane materials, and in particular, for the making of such castings which have excellent physical properties as well as good processing characteristics.
2. Description of the Prior Art
In the art of making polyurethane compositions, and in particular that of making of flexible polyurethane foams having improved load-bearing properties, it is known to use, for reaction with the polyisocyanate used in forming the polyurethane composition, a polyether polyol which is made by starting with an unsaturated polyol and grafting thereto, with the use of a free-radical catalyst, a proportion of units of ethylenically unsaturated monomer, such as acrylonitrile and/or styrene. Teachings of this sort may be found in U.S. Pat. No. 3,652,639. Example VIII of U.S. Pat. No. 3,652,639 describes the use of such an approach, even beyond the field of making flexible foams; it discloses the use of such an approach for the making of an elastomer composition.
In the art of constructing window frames, one prior-art practice is merely to make the frame of aluminum. This has the drawback that the frame readily conducts heat, thereby causing unwanted losses of heat to the exterior in cold weather and a corresponding drawback, with the heat flow in the opposite direction, during the summer air-conditioning season.
Noncellular, thermosetting polyurethane compositions have been made for use as castings, but in general, the mechanical and physical properties have been poor, especially if polymeric fillers are used.
To the applicants' knowledge, the prior art does not contain any teaching of how to provide a suitably strong, impact-resistant, thermosetting material with good handling characteristics, to serve as a heat barrier in the construction of window frames or the like, or in similar applications.